Russia said on Tuesday it had information that the United States planned to bomb the government quarter in Damascus on an invented pretext, and said it would respond militarily if it felt Russian lives were threatened by such an attack.
Valery Gerasimov, head of Russia's General Staff, said Moscow had information that rebels in the enclave of eastern Ghouta were planning to fake a chemical weapons attack against civilians and blame it on the Syrian army.
He said the United States intended to use the fake attack as a pretext to bomb the government quarter in nearby Damascus where he said Russian military advisers, Russian military police and Russian ceasefire monitors were based.
"In the event of a threat to the lives of our servicemen, Russia's armed forces will take retaliatory measures against the missiles and launchers used," Gerasimov said in a statement.
He did not say when the alleged attack would take place or provide detailed evidence to back his assertions.
In Washington, the Pentagon said Russia should focus on stopping Syrian President Bashar al-Assad from targeting innocent civilians.
"We urge Russia to stop creating distractions and compel the Assad regime to stop brutalizing innocent Syrian citizens and allow much-needed aid to reach the people of East Ghouta and other remote areas," Pentagon spokesman Eric Pahon said.
"By enabling the Assad regime's brutality, Russia is morally complicit and responsible for Assad's atrocities," Pahon added.